Ultrastructural analysis of platelets. (A) Electron microscopy of platelets (original magnification, × 7800) of a healthy individual and 2 heterozygous β1-tubulin Q43P carriers (carriers 1 and 2). Almost 50% of Q43P carrier platelets are enlarged and round (arrow). (B) Electron microscopy of platelets (original magnification, × 22 500) of a healthy individual and 3 heterozygous β1-tubulin Q43P carriers, showing cytoplasmic inclusions composed of smooth endoplasmic reticulum and abnormal membrane complexes (arrow). Note also the organelle-free zones in some platelets (arrowhead). There is a normal number of more centralized platelet alpha and dense granules.